Urinary Calculi and Endourology

EPIDEMIOLOGY OF STONES

Sex: men are affected thrice as commonly as women.

Age : Peak incidence is between 3rd to 5th decade.

Race ; Whites are affected 4 to 5 times in comparison to places.

Urolithiasis is a life long disease with an average of 9 year intervening between episodes.

ETIOLOGY AND PATHOGENESIS Development of stones in urinary tract is a complex, poorly

understood multifactorial process. Supersaturation

Ovur abundance of solute in solution. This occurs fairly well for uric acid, cysteine and xanthine

calculi. Inhibitiory substances in urine that black crystallization eg :

Pyrophosphates, citrate, zinc, magnesium; lack of sufficient urinary inhibition may cause precipitation of stones.

Matrix : Non crystalline mucoprotein often associated with urinary calculi. Pure matrix calculi may be seen in association

with proteus infection. Exogenous substances like indinavir and Triamterene may lead

to formation of stones.

STONES OF THE UPPER URINARY TRACT

Clinical presentation : Usually silent. When stone moves within urinary tract it produces either

haematuria, or some degree of urinary obstruction which may be accompanied by pain, urinary infection, generalized sepsis, nausea or vomiting.

Sudden onset, severe colicky in flanks or abdominal pain which may radiate to groin, testis , or tip of penis depending on the location of obstruction.

Gross or microscopic haematuria.

STONES OF THE UPPER URINARY TRACT

Diagnosis : Initial evaluation includes urinalysis, urine culture

and plain x-ray of KUB. Renal ultrasonogram demonstrates the presence of

stone along with any evidence of hydronephrosis if present.

Axial spinal CT confirmes the presence of calculus, and demonstrates the degree of obstruction.

Spiral CT is rapid, does not require bowel preparation and avoids use of IV & it has gradually replaced IVU as primary imaging modality for acute renal colic.

URINARY CALCULI AND COMPOSITION, FREQUENCY AND ETIOLOGIC FACTORS

S.No. Type of Stone Frequency Effect of pH Etiologic Factors

1.

a.

b.

c.

2.

3.

4.

5.

Calcium stones

Oxalate

Phosphate

Oxalate and Phosphate

Oxalate and Phosphate

Struvite

Uric acid

Cysteine

Other

Matrix

Xanthime

Triamtene

80%

35%

10%

35%

10%

8%

1%

1%

Solubility

Little effect

Increased at pH <5.5

Variable

Increaed at pH <5%

Increased at pH >6.8

Increased at pH >7.5

Supersaturation of urine with

calcium due to

1.Renal leak

2.Intestinal absorption.

3.Bone resorption.

Alkaline urine due to urea

splitting organisms.

Hyperuricosuria

Cystinuria

Alkaline urine due to urea

splitting organisms

STONES OF THE UPPER URINARY TRACT Treatment : Depends on size, location, degree of obstruction and patients clinical

status : Common sites of stone impaction are : Ureteropelvic junction . Pelvic brim where ureter crosses pelvic vessels. Ureterovesical junction. Patients with infection in high grade obstruction require prompt

intervention in the form of retrograde ureteral catheter or percutaneous nephrostomy drainage.

About 90% of ureteral calculi measuring less than 4 mm pass spontaneously whereas only 20% of calculi measuring more than 6 mm pass.

Expectant treatment in indicated in asymptomatic, non obstructed, non infective with stone size less than 4 mm diameter in the lower third of ureter.

STONES OF THE UPPER URINARY TRACT Treatment : Patient is asked to drink copious amount of water, four to six weeks

duration is allowed for passage of stone. Stone extraction is indicated for ureteral stones that do not pass

spontaneously. Small stones may be grasped directly or engaged in stone basket and

extracted. Longer stones may be fragmented using ultrasound, electrohydraulic, pneumatic or laser lithotripsy.

Shock wave lithotripsy is advantageous for urethral stones less than 8 mm diameter. It may be performed with or without a stent or long as stone can be adequ .ately visualized

Patients are often placed in prone position for distal ureteral stones. Ureterolithotomy is rarely needed given the high success rate of non-

operative and minimally invasive technique like SWL, ureteroscopy and laparoscopy.

BLADDER STONES

Clinical presentation Pain felt in hypogastrium or referred to penis. Intermittent stream. Dysuria. Haematuria. Recurrent urinary tract infections.

Commonly found in male patients of western world and increase the risk of sqaumous metaplasia or carcinoma in long standing case.

BLADDER STONES Diagnosis : Plain x-ray of KUB Bladder ultrasonography Cystoscopy Treatment : Lithotrites : Mechanical devices that permit crushing of large, hard, bladder stones,

under direct vision. It should be done only with bladder partially filled to prevent bladder wall injury. Fragments are then worked out through a resectoscope sheath.

Electrohydraulic Lithotripsy : Hydraulic shock wave is produced near stone that usually produces fragmentation after delivery of several shocks.

Ultrasound Lithotripsy is based on ultrasound energy delivered through a rigid probe passed through an endoscope causing fragmentation of stone which is removed by continous suction.

Cystolithotomy : It is performed through a small suprapubic incision. It has advantage of removing the entire store rather than leaving the fragments inside the bladder.

BLADDER STONES Treatment : Lithotrites : Mechanical devices that permit crushing of large,

hard, bladder stones, under direct vision. It should be done only with bladder partially filled to prevent bladder wall injury. Fragments are then worked out through a resectoscope sheath.

Electrohydraulic Lithotripsy : Hydraulic shock wave is produced near stone that usually produces fragmentation after delivery of several shocks.

Ultrasound Lithotripsy is based on ultrasound energy delivered through a rigid probe passed through an endoscope causing fragmentation of stone which is removed by continous suction.

Cystolithotomy : It is performed through a small suprapubic incision. It has advantage of removing the entire store rather than leaving the fragments inside the bladder.

RECURRENT STONE DISEASE

Diagnosis : Predisposing factors can be found in 80% of

recurrent stone for . mation Passage of single stone is an indication of screening study including determination of serum calcium, phosphorus, uric acid and 24 hourly urinary creatinine, calculi phosphorus, uric acid and oxalate levels.

Patients found to have any abnormality should have an extensive evaluation.

RECURRENT STONE DISEASE METABOLIC EVALUATION : Baseline studies already mentioned are performed & along

with recording of urinary patient. Dietary restriction of calcium to 400 mg and 100 mEq of

sodium for 1 week is done, followed by urine and serum studies as previously described.

CALCIUM LOADING : After on overnight fast during which only distilled water is

permitted patient reports at the clinic at 7 am. First urine sample is discarded, a 2 hour pooled specimen is

collected from 7 to 9 am. Patient receives 1 gm of calcium gluconate orally at 9 am and

collected of the urine specimen from 9 am to 1 pm in done.

HYPERCALCIURIA Resorptive hypercalciuria : Constant hypercalcuria

regardless of dietary restriction. Hyperparathyroidism is a common cause and causes calcium urolithiasis. Other causes include neoplasm metastatic to bone, multiple myeloma, immobilization, ’Cushing s disease etc. Treatment is by correction of the underlying disorder.

Absorptive Hypercalciuria : It is the most common cause and is responsible for formation of stones in more than 50% of patients. These patients have an exaggerated intestinal

response to vitamin D leading to hyperabsorption of ingested calcium. Urinary calcium normalizes on restriction of oral calcium and increases to abnormal range under calcium loading.

HYPERCALCIURIATreatment : Diet and hydration.

Patients should be placed on a diet restricted to 400 mg of calcium per day & 100 meq of sodium per day.

Addition of bran in useful as it binds calcium in the gastro intestinal tract. Drinking of 3 to 4 litres of water daily to reduce urinary concentration of

calcium. Cellulose phosphate : It is a calcium binding resin that exchanges sodium for

calcium in the gastrointestinal tract. It must be used in conjunction with calcium restricted diet.

Orthophosphates : They act by decreasing urinary excretion of calcium and increasing excretion of citrate and pyrophosphate both of which act to inhibit calcium stone formation.

Renal Hypercalciuria : This disorder is caused by inability of kidney to absorb calcium from tubular fluid. Thus, placing the patient on calcium restricted diet will not reduce loss of calcium in the urine. Calcium loading may increase urinary calcium even further.

HYPERURICOSURIAPure uric acid stones account for approximately 10% of calculi. Uric acid

becomes insoluble in urine at pH less than 5.8.ETIOLOGY : Approximately 25% of patients with uric acid calculi are found to have

gout. However most of them neither have hyperuricemia or hyperuricosuria. Calculi are probably caused by constantly acidic urine, dehydration or

both.Treatment : Hydration : Oral intake of atleast 3 litres water daily. Alkalinization of urine is usually achieved by oral or I.V. sodium

bicarbonate. Reduction of uric acid load may be achieved by dietary restriction and

use of allopininol. It is indicated in patients urine passive to hydration and alkalination of urine, who have meloproliferative disorders, those receiving chemotherapy.

HYPEROXALURIAOxalic acid is an extremely insoluble end product of metabolism. Primary hyperoxaluria : Autosomal recessive disorder

characterized by early onset of nephrocalcinasis due to enzymatic defect. Widespread deposition of oxalate in the kidneys and other soft tissue eventually occurs. Pyridoxine daily has reported reduction in oxalate excretion in some patients.

Enteric Hyperoxaluria : May occur in patients with malabsorption from any cause like inflammatory bowel disease, small bowel bypass surgery. Increased amount of fatty acids in bowel binds calcium leaving increased oxalate for absorption. Treatment includes low oxalate, low fat diet with oral fluid hydr ation and calcium supplementation. Cholestyramine binds oxalate and has good results in patients with malabsorption.

Exogenous hyperoxaluria : When substances metabolized to oxalate are ingested in large quantities such as ethylene glycol, as carbolic acid etc.

STRUVITE STONES Composed of magnesium ammonium phosphate and

carbonate. They may grow to fill the entire renal pelvis and collecting

system. They form when urinary pH is markedly elevated and increased

concentration of ammonia, carbonate & bicarbonate are present in the urine. Such conditions are caused by urea splitting organism s producing urease enzyme. Proteis species are most common with others like Klebsiella, pseudomonas etc.

Female are affected more in ratio of 2:1 as compared to males Other at risk group are spinal cord injury patients, patients

having indwelling catheter for many year, patients with ileal conduit and other supravesical diversions

STRUVITE STONES

Diagnosis : Struvite stones should be suspected in

any patient with high urinary pH caused by infection.

Plain X-ray of KUB will usually demonstrate the calculi.

IVU should be performed to determine whether obstruction is present and causing persistence of infection.

STRUVITE STONESTreatment : Aim of treatment is to achieve complete elimination of stones,

correction of any obstruction and eradication of infection. Surgical Modalities :

Nephrolithotomy. Nephrectomy in case of little or no renal function. Partial staghorn causing renal parenchymal damage requires

partial nephrectomy. Percutaneous lithotripsy : Recently it has replaced open surgery in

many patients and approximately 85% of patients can be rendered stone free at 3 months.

ESWL : ESWL alone produces stone free rates in range of 40 to 60% and multiple treatments are usually required. Sandwich technique used effectively involves percutaneous lithotripsy, followed by ESWL followed by secondary percutaneous lithotripsy, extraction on chemolysis.

STRUVITE STONESCHEMOLYSIS : Generally ineffective in calcium stones but can be used very effectively

to dissolve uric acid, cysteine, struvite and carbonate stones. Uric acid and cysteine stones : They are readily soluble in alkaline

solution by local irrigation through urethral or ureteral cather / Nephrostomy. Uric acid stones can be treated with solution of sodium bicarbonate in normal saline. Oral alkalinizing agent such as potassium citrate are better tolerated for long term maintenance of an alkaline .pH Cysteine stones may be treated with solution containing acetylcysteine, sodium bicarbonate and normal Saline.

Struvite and carbonate apatite calculi. They are amenable to dissolution by acidic solution having pH of less than 5.5. The most widely used solution is 10% hemiacridin delivered to store via nephrostomy tube or ureteral catheter. Normal saline infusion should be done priorly to determine response of collecting system.

STRUVITE STONESImportant precautions while doing chemolysis : Intrapelvic pressure must be below 30 cm ,water monitored

through a manometer. Treatment should be discontinued if patient complaints flank pain.

Infusate must have adequate egress which may be a problem in infusion through a single ureteral catheter.

Chemolysis is contraindicated in presence of urinary tract infection .

Hemocridin contains magnesium that can be absorbed to cause hypermagnesemia.

Prevention : Prevention of struvite calculi depends an elimination of infection with urea splitting organism . s Urease inhibitor such as acetohydroxamic acid may be used to decrease urinary pH and ammonia levels.

RENAL TUBULAR ACIDOSIS

Urolithiasis occurs only in type I, a disorder in which distal tubule is unable to maintain adequate hydrogen ion gradients. It accounts for approximately 1% of calcium stone forming patients.

ENDOUROLOGIC TECHNIQUES

Percutaneous access to the upper urinary tract is the cornerstone of endourologic technique.

The combination of rigid and flexible endoscopes with ultrasound or electrohydraulic lithotripsy allows virtually all stones to be treated by percutaneous means. It offers lower cost discomfort and reduced recovery time in comparison with open surgery.

ENDOUROLOGIC TECHNIQUES Percutaneous puncture techniques

patient is placed on fluroscopy table in prone position and imaging of kidney is carried out by fluoroscopy on ultrasonography.

Puncture site is most commonly on posterior axillary line midway between 12th rib and iliac crest.

Nephrostomy tube is placed through a renal pyramid into a p osterior calyx

ENDOUROLOGIC TECHNIQUES Ultrasound Lithotripsy :

High frequency sound waves cause fragmentation after delivery through a rigid probe passed through nephroscope.

Small fragments are removed by continuous suction.

Larger fragments are extracted with grasping forceps or stone baskets under di rect vision.

ENDOUROLOGIC TECHNIQUES Electrohydraulic lithotripsy –

Useful in stones resistant to US lithotripsy. Hydraulic shock wave is produced near stone

producing fragmentation. Its probe is flexible and can be passed through both

rigid and fibreoptic endoscopes. Fragments produced tend to scatter widely and

retrieval is not as easy as with US lithotripsy. Pneumatic Lithotripsy – Delivery of jack hammer effect

with compressed in causing stone fragmentation. Laser Lithotripsy – Holmium laser in used which is an

effective incisor of tissue and additionally may be used for cutting scars and uretheral strictures.

EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY It was developed in Germany in the early 1980s. Propogation of focussed shock wave through the body, which

fragment the stones. Shock is produced by either discharging a high voltage or

deforming a piezocrystal or moving a membrane by electromagnetic energy.

Average patient requires 1000 to 4000 shocks to fragment stones completely.

In some cases fragments may cause obstruction of the ureter. Combination of percutaneous techniques may be required to

reduce large staghorn calculi to smaller fragments before ESWL is performed.

Third generation machines are characterized by more compact designs, lower pressure and narrower focussing allowing anaesthesia free lithotripsy.

CONTRAINDICATIONS OF ESWL

Infundibular obstruction. Obstruction of ureter Active urinary tract infection.